Two powerful German guns control the seas past the Greek island of Navarone making the evacuation of endangered British troops on a neighboring island impossible. Air attack is useless so a team of six Allied and Greek soldiers is put ashore to meet up with partisans to try and dynamite the guns. The mission is perilous enough anyway but are the Germans on the island getting further help too?.
The year is 1943, and 2000 British soldiers are holed up on the island of Keros in the Aegean. Rescue by the Royal Navy is impossible because of massive guns on the nearby island of Navarone. Time is short, because the Germans are expected to launch an assault on the British forces, to draw Turkey into the war on the Axis' side.Efforts to blast the guns by air have proven fruitless, so a team has been hastily assembled to sail to Navarone and blow up the guns. Led by Major Roy Franklin (Anthony Quayle), they are Capt. Keith Mallory (Gregory Peck); Andrea Stavros (Anthony Quinn), a Colonel in the defeated Greek army; Corporal Miller (David Niven), an explosives expert; Greek-American street tough Spyros Pappadimos (James Darren); and "Butcher" Brown (Stanley Baker), an engineer and expert knife fighter.Disguised as Greek fishermen on a decrepit boat, they sail across the Aegean Sea. They are intercepted by a German boat and boarded. On Mallory's signal, they attack and kill all the Germans and blow up the patrol boat. Afterwards, Mallory confides to Franklin that Stavros has sworn to kill him after the war, because he was inadvertently responsible for the deaths of Stavros' wife and children.Their landing on the coast that night is hampered by a violent storm. The ship is wrecked and they lose part of their equipment, most notably the food and medical supplies. Franklin is badly injured while scaling the cliff, the injury later becoming infected with gangrene. They find that the cliff is in fact guarded after all. Miller, a friend of Franklin, suggests that they leave Franklin to be "well cared for" by the enemy. Mallory, who assumes command of the mission, feels that Franklin would be forced to reveal their plans, so he orders two men to carry the injured man on a stretcher.After Franklin tries to commit suicide, Mallory lies to him, saying that their mission has been "scrubbed" and that a major naval attack will be mounted on Navarone. Attacked by German soldiers, they split up, leaving Andrea behind with his sniper rifle, while they move on to their next rendezvous point. They contact local resistance workers, Spyros's sister Maria (Irene Papas) and her friend Anna (Gia Scala), who was supposedly rendered mute by the trauma of the Germans' torture.After meeting up with Maria and Anna, the team's mission is continually dogged by Germans, eventually being captured by Lieutenant Muesel (Walter Gotell) when they try to find a doctor for Franklin. Muesel and later Captain Sessler (George Mikell) of the SS fail to persuade the commandos to tell them where Miller's explosives are. Stavros pretends to betray the others and instead attacks the Germans, allowing the group to overpower their captors.They take the Germans' uniforms and escape, but leave Franklin behind so he can get medical attention. Franklin is injected with the truth drug scopolamine by Sessler and gives up the false "information", as Mallory had hoped. As a result, German units are deployed away from the guns and in the direction of the supposed "invasion" point.While making final preparations, Miller discovers that most of his explosives have been sabotaged and deduces that Anna is the saboteur. Not only is she the saboteur, but she can speak, and was never tortured by the Nazis; instead, she agreed to become an informer in exchange for her release. She pleads that she was coerced by the Germans into treachery, but while Mallory and Miller argue over her fate, complicated by Mallory's feelings for Anna, Maria shoots her dead. The team splits up. Mallory and Miller go for the guns, while Stavros and Pappadimos are to create a distraction in the city; Maria and Brown are assigned to steal a boat for their escape.Mallory and Miller make their way into the heavily fortified gun emplacements. Locking the main entrance behind them — which sets off an alarm alerting the Germans to their presence — Mallory and Miller set obvious explosives on the guns and hide more below an elevator leading to the guns. The Germans finally cut through the thick emplacement doors, but Mallory and Miller make their escape by diving into the sea. Despite Miller's inability to swim, they make it to the stolen boat, but learn that Pappadimos and Brown have been killed. Stavros is wounded and has difficulty swimming, but Mallory manages to pull him in.The destroyers appear on schedule. The Germans remove the explosives planted on the guns and fire. The first salvo falls short. The second brackets the lead ship. However, just as the guns are prepared to fire again, the elevator descends low enough to trigger the hidden explosives. The guns and fortifications are destroyed in a spectacular explosion. Franklin hears it from his hospital bed and smiles.Stavros, who has fallen in love with Maria, decides to return to Navarone with her and shakes hands with Mallory, having given up his planned vengeance.